REALEASE™
Alain Aronica, Charles Baldwin, Brad Devine, Graham Rose
Ferro France – 43, rue Jeanne d’Arc – 52100 Saint-Dizier – France
Ferro Corporation – 4150 east 56^th Street –Cleveland Ohio 44101 - USA
Ferro England – Nile Street – Burslem – Stoke-on-trent – ST6-2BQ - England

he properties and performance of Ferro’s non-stick coating will be discussed as well as the advantages versus conventional organic coatings and porcelain enamel.

Introduction
Because it is a glass-based coating, porcelain enamel is much more scratch, abrasion, and heat resistant than organic paints. Yet, burned on food residue forms hydrogen bonds and strong adheres to enamel [1]. The cleanability of enamel can be improved by maximizing the acid resistance, catalyzing the transformation of burned on residue into ash, pyrolyzing the residue into ash [2], or applying an easy-to-clean top-coat to the enamel [3,4]. However, none of these have the cleanability of organic non-stick coatings.
The two major families of organic non-stick coatings are those composed of either fluoropolymers such as polytetrafluoroethylene (PTFE) or of silicone-polyesters. PTFE-based coatings have been widely used on cookware, bakeware, and small appliances. Middle market PTFE coatings are two-ply with a binder-containing base coat and a fluoropolymer-rich finish coat. The most durable PTFE coatings for high-end cookware are three-coat systems with a ceramic oxide-containing intermediate coat for scratch resistance [5]. Silicone-polyesters are widely used on the exterior of cookware in a variety of colors. These two families of organic materials have a low surface energy in common, which prevents the adhesion of burned-on foods. Thus, residue can be removed with the application of minimal force using, for example, only water and a paper towel. However, both types of coating are soft and easily scratched or gouged. The abrasion resistance of the PTFE coatings tends to be much less than porcelain enamel. Additionally, there are two health and environmental concerns with PTFE. The first involves a surfactant used in the manufacture of fluoropolymer resins, but this material is unlikely to be present in cured PTFE coatings [6]. The second is the emission of toxic by-products by PTFE during thermal decomposition, which can occur if, for example, cookware is overheated [7].
RealEase™ marries the cleanability of the fluoropolymers and silicones to the durability of vitreous enamel. In a single coat, it offers the scratch resistance of enamel and the cleanability of PTFE. It is a patented technology that stands to bridge the gap between the organic non-sticks and low temperature porcelain enamel.

Processing
RealEase™ is applied to degreased and roughened aluminum, aluminized steel, brass, or copper.
Unlike conventional enamel, it can be applied to die-cast aluminum. Roughening can be done with sandblasting or acid etching. It can be applied to mild steel, stainless steel, cast iron, glass or ceramics after the application of special patented hard-bases. Hard-bases are an enamel base coat with a rough surface [8].
RealEase™ is supplied as a wet ready-to-use (RTU) system. The RTU slip requires no adjustment of set, gravity, or color. Like enamels and unlike PTFE, the overspray can be reclaimed and re-used at 30%. The coating is dried at about 125ºF (52ºC). Once dried, it may be screen printed with other RealEase™ colors and fired in a single process. The coating fires at about 878ºF (470ºC).
The time varies with the metal thickness and thermal conductivity. A convection type oven is preferred. Volatile emissions during curing are 70 to 80% less than PTFE.

Fired Properties
Typically, RealEase™ is about 2 mils (50-60 μm) thick without hard-base and as low as 1.5 mils (40 μm) with hard-base. The hard-base is typically 1.5 mil (40 μm) thick and requires an additional fire.
RealEase™ can be supplied in many colors except bright white. Generally, the color palette is similar to that for aluminum enamels. It has a satin finish with a 60° gloss of 2 – 10, depending on firing conditions. Possible effects are mottles, stipples, shadow application, and recently developed metallic colors. Examples of metallic RealEase™ colors are shown in Figure 1.

Figure 1. Examples of metallic RealEase™

RealEase™ has lower surface than conventional enamel and is therefore hydrophobic and easy-toclean. The balance of forces arising from a sessile drop of liquid water, l, on the coating surface, s, under a vapor, v, is schematically shown in, and is described with Young’s equation

where γ is the energy per unit area of the appropriate interface and θ is the contact angle between the liquid and the substrate. If γ_s/v > γ_s/l, the surface will be wetted to decrease the area of the higher energy s/v interface; this is the situation with conventional enamel. If γ_s/v < γ_s/l, balling up of the water will occur to reduce the area of the higher energy s/l interface.

Figure 2. Liquid droplet on a hydrophobic surface [9]

Typically, θ is only 60° for conventional enamel, about 120° for PTFE, and about 110° for RealEase™. This is shown in Figure 3. Droplets of water wet and spread on a dual-purpose black ground coat. On RealEase™, they are repelled by the surface and form beads.

Figure 3. Wetting on (a) conventional enamel and (b) RealEase™

The cleanability has been assessed by the European FAN (Facile à Nettoyer, literally Easy-to-Clean) test. First, five steel rings are glued to the coating surface. Second, salted whole milk, gravy, lemon juice, egg yolk, and ketchup are placed in each ring. Third, the test panel is baked at 482°F (250°C) for 30 minutes. Then, the glue thermally decomposes, which allows the ring to be removed. Finally, the cleaning is rated using the system shown in Table 1.

The results for RealEase™, PTFE, stainless steel, and a typical porcelain enamel are shown in Figure 4. RealEase™ achieves a perfect score and shows cleanability equal to PTFE and much better than stainless steel or traditional enamel.

Figure 4. Cleanability results

RealEase™ exhibits good acid and alkali resistance. It achieves a AA rating on the PEI T-21 citric acid spot resistance test. It is UV stable and unaffected by solvents. It has excellent scratch and abrasion resistance.
Scratch resistance is evaluated using ASTM D 3363-00 “Standard Test Method for Film Hardness by Pencil Test.” The force required to gouge a coating with a drawing lead of calibrated hardness is assessed. RealEase™ shows a rating of 8H compared to an average of 4H for PTFE coatings.
Results are shown in Figure 5.

Figure 5. RealEase™ pencil hardness

Abrasion resistance is measured using ASTM D 4060-95 “Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser.” The weight loss before and after 2000 cycles under the most abrasive CS-17 wheels under a 1 kg was measured and normalized to the coating thickness. Results are shown in Figure 6. On average, RealEase™ was less damaged by abrasion than PTFE and significantly less than silicone-polyesters.

Figure 6. Taber abrasion results

RealEase™ has more heat resistance than the organic non-stick coatings. It can be used in service at 600°F (315°C) for extended periods of time. Figure 7 shows the color stability of RealEase™ compared to a high-temperature silicone-polyester paint. After 100 hours at either 662°F (350ºC) or 752ºF (400ºC), RealEase™ showed little color change versus a ΔE as high as 51.17 for the siliconepolyester after 100 hours at 752°F (400°C). PTFE shows similar degradation at elevated temperatures.

Figure 7. Color stability of RealEase™ versus silicone paint

ceramic bakeware. RealEase™ is listed with the National Sanitation Foundation (NSF) as compliant with Standard 51. It is certified as safe for food contact (acidic, aqueous, < 8% alcohol beverages, dairy, dry solids, and other) up to 750°F [10]. With superior heat resistance, it is very promising for heavy-duty use environments such as commercial kitchen restaurants. It could be used on small appliances such as toaster ovens and microwaves. It is an alternative to silicone-polyesters and PTFE on grills, griddles, and simmer plates.
In summary, RealEase™ is a water-based non stick coating applied as a single coat. Compared to silicone-polyesters and PTFE, it is much more scratch resistant, more abrasion resistant, and more heat resistant.